In the study of soil fertility, biological factors, especially the microbiological activity of soils, have recently attracted increasing attention. Agronomically important groups of microorganisms that participate in the nitrogen and carbon cycle play an important role in soil fertility. By the number of these organisms, it is possible to indicate the state of the soil and characterize the direction of the processes occurring in it. In this regard, it seemed to us necessary to carry out a quantitative account of the main physiological groups of microorganisms involved in the transformations of nitrogen- and carbon-containing substances. The studied area is included in the semi-desert serozem zone with its characteristic geomorphology, climate and vegetation cover. Agrochemical, agrophysical, physical and chemical properties and the sum of integral indicators of the ecological and biological state of soils, it makes it possible to determine the level of impact of their ecological and genetic properties, as well as natural and environmental factors on soil fertility and land degradation.